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Replaced CAT On Project B5 RS4 "Outlaw" Sedan

Siena Aug 3, 2008

  1. Siena

    Siena Active Member

    Ever since I bought her, she's always had a nasty hollow sound, increases with revs.

    When cold, she was really noisy, only after a minute or so running, would she quieten down.

    I put her on the ramp last Monday, and discovered 2 things:

    The offside flexi joint was blowing badly, cracked almost all round, held together mostly by the braid.

    The offside catalyst had a welded "trapdoor", meaning one thing - it had been cut open, and gutted, hence the resonance.

    Got a catalyst, brand new, but for a Honda 2,0 16V V-tech unit for £40.
    Not worth going for the Sport catalyst system, and full custom stainless exhaust, as it'll need to be modified again, to suit the S8 motor.

    Modified it by cutting off the flanges both end, and welding pipework on to suit the Audi set-up, and fitted it yesterday.

    It was blowing from the front joint, so I re-sealed it today, with a couple of new 58mm clamps, and boy, does she sound good!

    I'll try putting up some sound clips later on.
  2. Andy.B

    Andy.B Member

    They had only gutted one cat?? thats a bit odd isnt it? Nice job robbing the Honda for a cat tho.

    ALPINE Yes its diesel, now cry u lost

    glad you stopped the blowing siena.... did sound a bit sore.

    not as sore as my arm trying to hack saw the old pipeage off tho!! (Alpine cut!)

    you should sell your gutted cat on Ebay... to suit saxo/corsa.. gutted cat off audi v6!! some mug would buy it! lol
  4. aragorn

    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

    i presume that if they;d gutted both cats it'd have failed the emissions tests, but with half the gas passing through a cat and half not, the resulting mix would probably have just about scraped thru?

    Still seems a weird thing to do unless they were intentionally trying to make it louder?
  5. Siena

    Siena Active Member

    I doubt the cat was gutted for performance.

    I imagine it developed a rattle, or collapsed, blocking flow, and it was gutted so the car could at least breathe, and run.

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